1. The Skeletal System Divided into two divisions
Axial skeleton – the skull, vertebral column & ribs
Appendicular skeleton – shoulder, arm, pelvis & legs
Slide 5.1
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

2. The Skeletal System Parts of the skeletal system Bones
Joints – give flexibility & allow movement
Cartilages – protects & cushions ends of bones
Ligaments – connects bones at joints
Slide 5.1
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

3. Functions of Bones Support of the body Protection of soft organs
Movement due to attached skeletal muscles
Storage of minerals and fats
Blood cell formation (hematopoiesis)
Slide 5.2
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

4. Bones of the Human Body Adult skeleton has 206 bones
Two basic types of bone (osseous) tissue
Compact bone
Homogeneous, dense
Spongy bone
Small needle-like pieces of bone
Many open spaces
Figure 5.2b
Slide 5.3
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

5. 4 Kinds of Bones - Based on Shape
Figure 5.1
Slide 5.4c
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

6. Classification of Bones
Long bones
Typically longer than wide
Have a shaft with heads at both ends
Contain mostly compact bone
Make up the bones in your arms & legs
Examples: Femur, humerus
Slide 5.4a
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

7. Classification of Bones
Short bones
Generally cube-shape
Contain mostly spongy bone
Examples: wrist bones (carpals), ankle bones (tarsals) and the patella (knee cap)
Slide 5.4b
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

8. Classification of Bones
Flat bones
Thin and flattened
Usually curved
2 thin layers of compact bone sandwich a layer of spongy bone
Examples: Skull, ribs, sternum (breast bone)
Slide 5.5a
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

9. Classification of Bones
Irregular bones
Irregular shape
Don’t fit into the other 3 bone categories
Example: Vertebrae and hip bones
Slide 5.5b
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

10. Gross Anatomy of a Long Bone
Diaphysis
Shaft (long part)
Compact bone
Center = fat storage
Epiphysis
Ends of the bone
Mostly spongy bone
Center = red marrow
Figure 5.2a
Slide 5.6
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

11. Structures of a Long Bone
Periosteum
Covers external surface of the diaphysis
Fibrous connective tissue membrane
Articular cartilage
Covers external surface of the epiphyses
Hyaline cartilage which decreases friction in joints
Figure 5.2a
Slide 5.8a
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

12. Bone Markings
Surface of a bone is not smooth but scarred with bumps, holes & ridges
This is where muscles, tendons, and ligaments attach
They are also openings for nerves and blood vessels to run through
Slide 5.9
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

13. Bone Markings Categories of bone markings
Projections and processes – grow out from the bone surface
Depressions or cavities – indentations or even holes in the bone
Slide 5.9
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

14. Microscopic Anatomy of Bone
Figure 5.3
Slide 5.10b
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

15. Microscopic Anatomy of Bone
Compact bone looks dense and simple
Actually a very complex system of tiny cavities (lucunae) that are arranged in concentric circles (like tree rings)
Canals run through this complex system to bring in blood supply, nourishment, take out waste, etc
Mature bone cell is called an osteocyte
Figure 5.3
Slide 5.11a
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

16. Changes in the Human Skeleton
Skeleton is formed from two of the strongest & most supportive tissues: cartilage and bone
In embryos, skeleton is mostly hyaline cartilage
In a young child, most of this cartilage is replaced by bone
Hyaline cartilage remains in isolated areas
Bridge of the nose, parts of ribs, joints
Slide 5.12
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

17. Long Bone Formation and Growth
Figure 5.4a
Slide 5.14a
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

18. Bone Growth
Epiphyseal (growth) plates allow for growth of long bones during childhood
New cartilage is continuously formed while older cartilage becomes ossified or changed to bone
Causes bones to grow in length but also causes bone to grow wider (appositional growth), so calcium in puberty is really important especially for girls
Growth is happening at both ends of the bone; can lead to “growing pains”
Slide 5.13a

19. Long Bone Formation and Growth
Figure 5.4b
Slide 5.14b
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

20. Bone Growth After puberty, bone growth stops
The epiphyseal plate becomes bone
Leaves a line on the long bone between the diaphysis and epiphysis
Can see the epiphyseal line on an x-ray & know when a kid is done growing
Always a concern if a younger kid breaks an arm or leg and the break goes into the growth plate
Slide 5.13a
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

21. Types of Bone Cells Osteocytes Osteoblasts Osteoclasts
Mature bone cells
Osteoblasts that become trapped in matrix
Osteoblasts
Bone-forming cells
Osteoclasts
Bone-destroying cells
Break down bone matrix for remodeling and release of calcium
Slide 5.15
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

22. Bone Growth
Bones are remodeled and reshaped by the osteoblasts and osteoclasts.
Necessary during growth so bones keep normal proportions and strength.
Bones become thicker and stronger where larger muscles need to attach
If bedridden or inactive, bones atrophy or shrink because there’s no stress. This is a problem for astronauts and the aging.
Slide 5.13b
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

23. Bone Growth Bones grow and remodel according to 2 factors:
Pull of gravity & muscles on the skeleton
More stress = more bone, less stress = less bone
Calcium levels in the blood
If too low, the parathyroid gland releases PTH into blood and activates the osteoclasts
If too high, calcium is deposited into the bone matrix
Slide 5.13b
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

24. Rickets Slide 5.16 Soft bones because the bones don’t calcify
Occurs in children due to lack of calcium or lack of vitamin D which is needed for calcium to be absorbed into the bloodstream
Results in bowed legs – can be a severe amount
Not an issue in U.S. since many foods are fortified with vitamin D and kids drink milk
Slide 5.16
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

25. Bone Fractures Slide 5.16 A break in a bone Types of bone fractures
Closed (simple) fracture – break that does not penetrate the skin
Open (compound) fracture – broken bone penetrates through the skin
Common types are: comminuted, compression, depressed, impacted, spiral and greenstick
Slide 5.16
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

26. Slide 5.17 Common Types of Fractures Table 5.2
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

27. Repair of Bone Fractures
First the fracture or break must be reduced (the bones need to be moved back into their correct place)
Many simple fractures reduce themselves or can be coaxed by the doctor’s hands
Some simple and most compound fractures require surgery & the use of pins, wires, plates, etc.
Slide 5.18
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

28. Repair of Bone Fractures
Next the fracture or break must be immobilized.
This is often done with a cast, but may use a brace, traction, halo, etc.
Young kids can heal in 4 weeks, simple fractures in adults take 6-8 weeks and more serious fractures or fractures in the elderly can take months.
A fracture when pregnant may not heal correctly because of the baby.
Slide 5.18

29. Steps in healing a Bone Fracture
Hematoma (blood-filled swelling) is formed during break, so bone cells die
A mass of repair tissue (fibrocartilage callus) forms to splint the break; contains capillaries, granulation tissue, phagocytes and connective tissue
Bony callus (spongy bone) replaces fibrocartilage callus
Bony callus is remodeled to form a permanent patch of compact bone
Slide 5.18

30. Slide 5.19 Stages in the Healing of a Bone Fracture Figure 5.5
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings